Evaluation of the i-STAT point-of-care capillary whole blood hematocrit and hemoglobin: Comparison to the Siemens RAPIDLab 1200, Sysmex XE5000, and manual spun hematocrit

Background: Conductivity based point-of-care hematocrit with calculated hemoglobin devices serves an important role in clinical scenarios where time sensitive transfusion decisions are necessary. However, questions about the appropriateness of conductivity based assays in certain patient populations (patients on cardiopulmonary bypass and those receiving high volumes of intravenous fluids or autologous blood transfusions) have been raised. The clinical suitability of POC devices for these applications necessitates that they be accurate and that the results are interchangeable with central laboratory methods. Methods: We performed hematocrit and hemoglobin analysis on 225 clinical samples using the i-STAT instrument, a standard reference method for hematocrit (manual spun) and other common methods on both cardiopulmonary bypass and non-cardiopulmonary bypass patients. Results: The i-STAT hematocrit and hemoglobin showed close agreement to comparison methods with minimal bias. Median test results were not clinically or statistically different between those measured on the i-STAT and those measured using the manual spun hematocrit reference method (p. = 0.4085, Wilcoxon signed rank test) or the Sysmex photometric hemoglobin method (p. = 0.2728, Wilcoxon signed rank test). The results on the i-STAT were statistically different from those obtained on the Sysmex for hematocrit (p. <. 0.0001) and the Siemens RAPIDLab co-oximeter for hemoglobin (p. <. 0.0001). Conclusion: The i-STAT hematocrit and hemoglobin performs well when compared to the hematocrit reference method and other common methods for both hematocrit and hemoglobin. Some differences between non-reference methods may be observed, but these were not considered clinically significant.